There are a compressed air drive nailing machine for driving a piston at inside of a cylinder by introducing compressed air to inside of the cylinder containing the piston and striking a nail to a struck member of wood or the like by a driver coupled to the piston, and a combustion gas drive nailing machine formed with a combustion chamber at inside of a housing for generating a combustion gas at high pressure at inside of the combustion chamber by injecting a combustible gas to inside of the hermetically closed combustion chamber and combusting the combustible gas, impulsively driving the piston at inside of the cylinder by operating the combustion gas to the piston slidably contained at inside of the cylinder and striking a nail to a steel plate, concrete, wood or the like by a driver coupled to the piston.
In such power drive nailing machines, a lower side of the housing containing the cylinder is coupled with a nose portion formed with the injection port for striking and guiding a nail to a work member. The driver coupled to a lower face of the piston contained at inside of the cylinder is contained at inside of the injection port to be guided thereby. A rear side of the nose portion is continuously provided with a magazine containing a number of nails. The nail supplied from the magazine to inside of the injection port of the nose portion is struck from the injection port to the struck member arranged at a front end of the nose by the driver.
The power drive nailing machine for driving the piston by the compressed air or the combustion gas as described above is provided with a contact member slidably supported along an outer peripheral face of the nose portion. Ordinarily, the contact member is arranged to project in a direction of a front end of the injection port. An upper end of a contact arm connected to the contact member is connected to be engaged with an activation control apparatus for activating the power drive nailing machine. When the power drive nailing machine is positioned to a nail striking position by bringing the nose portion of the power drive nailing machine into contact with the struck member, by engaging the contact member with the struck member to operate to slide along the nose portion, the activation control apparatus is operated by way of the contact arm, and the power drive nailing machine is set to a startable state.
JP-B2-3527571 discloses a power drive nailing machine formed with a strike depth adjusting apparatus for arbitrarily adjusting a depth of striking a nail at inside of an injection port to a struck member by a driver connected to a piston impulsively driven by compressed air or a combustion gas. According to the power drive nailing machine, a length of projecting a contact member can variably be adjusted such that a front end face of the contact member in being slid to move up to an upper dead center along a nose portion is made to constitute an arbitrary projected length from a front end face of the injection port of the nose portion. Therefore, a front end of the injection port: of the nose portion can be made to be spaced apart from a struck face of a struck member by an arbitrary interval. The strike depth adjusting apparatus is constituted by a plate-like portion extended from the contact member to an upper side, and a lower end portion of a contact arm an upper end of which is connected to be engaged with an activation control apparatus and formed in a plate-like shape. By bringing recessed and projected faces of numbers of streaks formed at respective faces of two sheets of plate-like members opposed to each other in mesh with each other at arbitrary positions, the two plate-like members are fixed by a screw or the like.
According to the strike depth adjusting apparatus in which the recessed and projected faces formed at the respective faces of the plate-like members opposed to each other are brought in mesh with each other and fixed by a screw or the like, when a user adjusts a strike depth, the screw fastening the plate-like members is relaxed by using a tool of a wrench or the like. After shifting the respective recessed and projected faces of two sheets of the plate-like members to be brought in mesh with each other again, the user fastens the screw by using the tool again. Therefore, there is a case in which an adjusting operation cannot be carried out in an operation above an unstable foothold. Further, in order to connect the contact member and the contact arm by the screw or the like, a portion of connecting these is arranged at a side face of the nose portion. Therefore, the contact arm is arranged to be bent relative to a direction of operating the contact member and a direction of operating the activation control apparatus. As a result, when the contact member is operated to slide along the nose portion, there is a case in which the contact arm is deformed and the operation of sliding the contact member cannot firmly be transmitted to the activation control apparatus, the power drive nailing machine cannot be activated or operated erroneously.